The understanding of the mechanisms of metabolic control is of paramount importance in comprehending normal and abnormal cellular growth and differentiation. With this in mind we have been examining the mechanism of multivalent repression in Escherichia coli and Salmonella Typhimurium. In this process regulation is accomplished by the intervention of a number of small and large molecules. This system, therefore, provides a model to study a regulatory process involved in the control of protein synthesis that receives and responds to signals from a number of cellular constitutents. We are studying the role of a number of compounds on translational and transcriptional control and their possible participation in in vitro and in vivo regulation. BIBLIOGRAPHIC REFERENCES: Favre, R., A. Wiater, S. Puppo, M. Iaccarino, R. Noelle and M. Freundlich. 1976. Expression of a valine-resistant acetolactate synthase activity mediated by the ilv o and ilv G genes of E. coli K-12. Molec. Gen. Genetics 143 (243-252). Childs, G., E. Ohtsubo and M. Freundlich. l976. Restriction endonuclease fragment maps of the E. coli chromosome in the vicinity of the ivl genes. Tenth International Congress of Biohemistry, Hamburg (Abstracts).